1. Field of the Invention
The present invention relates to a thermally assisted magnetic head recording data on a magnetic recording medium by thermally assisted magnetic recording using near-field light and a method of manufacturing the same, and a head gimbal assembly and a hard disk drive each having a thermally assisted magnetic head.
2. Related Background Art
In recent years, as hard disk drives have been increasing their recording densities, thin-film magnetic heads recording data on magnetic recording media have been required to further improve their performances. As the thin-film magnetic heads, those of composite type having a structure in which a reproducing head having a magnetoresistive device (hereinafter, referred to also as an “MR device”) for read and a recording head having an electromagnetic coil device for write are laminated have been conventionally in wide use. In a magnetic disk drive, the thin-film magnetic head is provided on a slider which very slightly floats from the magnetic recording medium.
Incidentally, the magnetic disk drive records data by magnetizing magnetic fine particles on the magnetic recording medium using the recording head. In order to increase the recording density of the magnetic recording medium, it is effective to make the magnetic fine particles smaller.
When the magnetic fine particles are made smaller, however, there arises a problem that the magnetization thereof becomes unstable with respect to heat as the particles reduce in volume, thereby increasing the possibility that the data recorded on the magnetic recording medium is lost. To solve the problem, it is effective to increase the magnetic energy of the magnetic fine particles to thereby enhance the stability of magnetization. When the magnetic energy of the magnetic fine particles is increased, however, there arises another problem that the coercive force (difficulty in reversing magnetization) of the magnetic recording medium increases to deteriorate the data recording performance.
To solve such problems, a method called thermally assisted magnetic recording has been conventionally proposed. When recording data on a magnetic recording medium having a large coercive force, the thin-film magnetic head employing the thermally assisted magnetic recording (hereinafter, referred to as a “thermally assisted magnetic head”) records data while instantaneously heating and thereby increasing the temperature of a portion of the magnetic recording medium where data will be recorded.
Since the magnetic fine particles decrease in coercive force when the temperature is increased, instantaneous heating makes it possible to record data even on the magnetic recording medium having a high coercive force at room temperature. The portion of the magnetic recording medium where the data has been recorded is decreased in temperature after the recording of data and thereby increases in coercive force. Therefore, by using the thermally assisted magnetic head, it becomes possible to make the magnetic fine particles finer as well as stabilize recording in the magnetic disk drive.
On the other hand, near-field light is used as means for heating the magnetic recording medium in the conventional thermally assisted magnetic head. When light enters an opening smaller than the wavelength of light, the light slightly seeps from the opening and locally exists near the opening. The light locally existing near the opening is called near-field light. The near-field light is confined in a region much smaller than that of a spot light obtained by collecting light using a lens, so that use of the near-field light makes it possible to heat only a limited extremely small recording region of the magnetic recording medium.
Known as a method of generating the near-field light in the conventional thermally assisted magnetic head is a method using a plasmon antenna (also called a plasmon probe) that is a minute metal piece. In this method, the near-field light is generated by guiding laser light to the plasmon antenna via an optical waveguide.
As a conventional plasmon antenna, a light scattering body made of metal such as gold, palladium or the like in a triangular thin plate structure is disclosed in Japanese Patent Application Laid-Open No. 2005-4901 (referred also to as patent document 1), for example. Further, a plasmon probe made of metal such as gold, silver, aluminum or the like in the shape of a triangle pole is disclosed in Japanese Patent Application Laid-Open No. 2007-257753 (referred also to as patent document 2). Furthermore, a near-field light generating part in an isosceles triangle including a tip end reaching a medium-opposing surface is disclosed in Japanese Patent Application Laid-Open No. 2007-164935 (referred also to as patent document 3). A near-field light generating part in a triangle pole shape formed on an optical waveguide is disclosed in Japanese Patent Application Laid-Open No. 2012-3830 (referred also to as patent document 4). A near-field light generating part in a triangle shape formed on an optical emitting surface of a medium-opposing surface side of an optical waveguide is disclosed in Japanese Patent Application Laid-Open No. 2008-257819 (referred also to as patent document 5).